Move empty_line_after_outer_attribute to nursery
Move empty_line_after_outer_attribute to nursery

From the clippy side it's difficult to detect empty lines between
an attributes and the following item because empty lines and comments
are not part of the AST. The parsing currently works for basic cases
but is not perfect and can cause false positives.

Maybe libsyntax 2.0 will fix some of the problems around attributes but
comments will probably be never part of the AST so we would still have
to do some manual parsing.

graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust